US8511216B2 - Hydraulic actuator unit - Google Patents

Abstract

A hydraulic actuator unit includes a first electric motor assembly formed by mounting one of a pair of electric motors to one of a pair of electric motor covers, wherein the first electric motor assembly is detachably mounted to a pump case so as to rotate a first control shaft around its axis line, and a second electric motor assembly formed by mounting the other one of the pair of electric motors to the other one of the pair of electric motor covers, wherein the second electric motor assembly is detachably mounted to the pump case so as to rotate a second control shaft around its axis line.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic actuator unit including a hydraulic actuator such as a hydraulic pump main body, variable displacement mechanism for changing a displacement of the hydraulic actuator, and an electric motor for actuating the variable displacement mechanism.

2. Related Art

With regard to a hydraulic actuator unit such as a hydraulic pump unit or an HST unit, which includes a hydraulic actuator such as a hydraulic pump main body and a variable displacement mechanism for changing a displacement of the hydraulic actuator, there has been proposed a configuration in which the variable displacement mechanism is actuated with use of an electric motor (for example, US Patent Application Publication No. 2006-0272495).

The conventional hydraulic actuator unit is useful in that operation force required for actuating the variable displacement mechanism could be reduced, since the electric motor actuates the variable displacement mechanism so as to change the displacement of the hydraulic actuator.

However, the hydraulic actuator unit disclosed in the US patent application publication has following problems.

The US patent application publication discloses the hydraulic actuator unit in the form of hydraulic pump unit.

Specifically, the hydraulic actuator unit includes a pump case, first and second pump shafts, first and second hydraulic pump main bodies, first and second variable displacement mechanisms, and a pair of electric motors. The first and second pump shafts are supported by the pump case in a rotatable manner around their respective axis lines in a state of being parallel to each other and being operatively connected to each other. The first and second hydraulic pump main bodies are accommodated in the pump case in a state of being supported by the first and second pump shafts in a relatively non-rotatable manner with respect thereto. The first and second variable displacement mechanisms change displacements of the first and second hydraulic pump main bodies, respectively. The pair of electric motors actuate the first and second displacement mechanisms, respectively.

The first pump shaft has first and second ends that are positioned on one side and the other side in its axis line direction, the first end being extended outward from the pump case to form an input end to be operatively connected to a driving power source. The second pump shaft has first and second ends that are positioned on the same side as the first and second ends of the first pump shaft with respect to the axis line direction, respectively, the second end being extended outward from the pump case to drive a cooling fan.

The first variable displacement mechanism includes a control shaft (hereinafter referred to as first control shaft) that is supported by the pump case in a rotatable manner around its axis line in a state where its first end is inserted into the pump case so as to be operatively connected to a corresponding variable swash plate and its second end is extended outward from the pump case.

The second variable displacement mechanism includes a control shaft (hereinafter referred to as second control shaft) that is supported by the pump case in a rotatable manner around its axis line and in parallel with the first control shaft in a state where its first and second ends are faced in the same direction as the first and second ends of the first control shaft. The first end is operatively connected to a corresponding swash plate, and the second end is extended outward from the pump case.

One (hereinafter referred to as first electric motor) of the pair of electric motors is mounted to the pump case via an electric motor cover (hereinafter referred to as first electric motor cover) so as to rotate the second end of the first control shaft around the axis line, while the other one (hereinafter referred to as second electric motor) of the pair of electric motors is mounted to the pump case via an electric motor cover (hereinafter referred to as second electric motor cover) so as to rotate the second end of the second control shaft around the axis line.

Specifically, the first electric motor cover supports the first electric motor so that an electric motor main body of the first electric motor is positioned on an opposite side to the first end of the first pump shaft with respect to a first virtual surface that passes through axis lines of the first and second control shafts.

On the other hand, the second electric motor cover is symmetrical to the first electric motor cover with respect to a second virtual plane that is orthogonal to the first virtual plane and passes through a center between the first and second control shafts. Specifically, the second electric motor cover supports the second electric motor so that an electric motor main body of the second electric motor is positioned on the same side as the second end of the second pump shaft with respect to the first virtual plane.

In the conventional hydraulic actuator unit with the configuration, the cooling fan has to be away from the pump case in such a manner as that the cooling fan, which is mounted on the second end of the second pump shaft, is not interfered with the second electric motor, resulting in an enlargement of the hydraulic actuator unit as a whole.

Moreover, as explained above, the first and second electric motor covers are symmetrical to each other with respect to the second virtual plane. Specifically, in the conventional hydraulic actuator unit, the first electric motor cover is exclusively used for mounting the first electric motor and the second electric motor cover is exclusively used for mounting the second electric motor, rather than the first and second electric motor covers have the same configuration to each other.

Accordingly, in the conventional hydraulic actuator unit, it is likely to cause a mistake in assembling work of the first and second electric motors to the pump case, resulting in worsened assembling workability of the first and second electric motors while involving complicated inventory management of the first and second electric motor covers.

Furthermore, the conventional hydraulic actuator unit does not take into account cases where the variable displacement mechanism needs to be manually operated upon breakdown or mode change of the electric motor. Therefore, the conventional hydraulic actuator unit has difficulties in changing modes between the electric mode of actuating the variable displacement mechanism with use of the electric motor and the manual mode of manually actuating the variable displacement mechanism.

SUMMARY OF THE INVENTION

The present invention is made in view of the prior art, and it is a first object to provide a hydraulic actuator unit including a pump case, first and second pump shafts that are supported by the pump case in a rotatable manner around respective axis lines in a state of being positioned in parallel to each other and being operatively connected to each other, first and second hydraulic pump main bodies that are accommodated in the pump case in a state of being supported by the first and second pump shafts respectively in a relatively non-rotatable manner with respect thereto, first and second variable displacement mechanisms that change displacements of the first and second hydraulic pump main bodies, respectively, and first and second electric motors that actuate the first and second variable displacement mechanisms, respectively, wherein the first pump shaft has a first end extended outward from the pump case so as to be operatively connected to a driving power source and a second end on an opposite side to the first end, and wherein the second pump shaft has first and second ends that are positioned on the same side as the first and second ends of the first pump shaft in the axis line direction, the second end being extended outward from the pump case to drive a cooling fan, the hydraulic actuator unit capable of being miniaturized as a whole while achieving common use of components as much as possible.

In order to achieve the first object, the present invention provides a hydraulic actuator unit including a pump case, first and second pump shafts that are supported by the pump case in a rotatable manner around respective axis lines in a state of being positioned in parallel to each other and being operatively connected to each other, first and second hydraulic pump main bodies that are accommodated in the pump case in a state of being supported by the first and second pump shafts respectively in a relatively non-rotatable manner with respect thereto, first and second variable displacement mechanisms that change displacements of the first and second hydraulic pump main bodies, respectively, and first and second electric motors that actuate the first and second variable displacement mechanisms, respectively, the hydraulic actuator unit being characterized in that the first pump shaft has first and second ends positioned on one and the other sides in its axis line direction, the first end being extended outward from the pump case to form an input end that is operatively connected to a driving power source, the second pump shaft has first and second ends that are positioned on the same side as the first and second ends of the first pump shaft in the axis line direction, the second end being extended outward from the pump case to drive a cooling fan, the first and second variable displacement mechanisms include first and second movable swash plates each of which changes a displacement of the corresponding hydraulic pump main body in accordance with its slanting position around a swing axis line, and first and second control shafts each of which is supported by the pump case in a rotatable manner around its axis line, each of the first and second control shafts has a first end operatively connected to the corresponding movable swash plate in such a manner as to slant the movable swash plate in accordance with its rotation around the axis line and a second end extended outward from the pump case, the first and second control shafts are supported by the pump case in such a manner as that they are orthogonal to the first and second pump shafts and their second ends are faced in the same direction to each other, each of the pair of electric motors has an electric motor main body that is controlled and driven based on an external electric signal, an electric motor output mechanism that is operatively connected to an output shaft of the electric motor main body, and an electric motor case that supports the electric motor main body and the electric motor output mechanism, the hydraulic actuator unit further includes a pair of electric motor covers for connecting the pair of electric motors to the pump case, one of the pair of electric motors is mounted to one of the pair of electric motor covers to form a first electric motor assembly that is detachably mounted to the pump case so as to rotate the first control shaft around the axis line, the other one of the pair of electric motors is mounted to the other one of the pair of electric motor covers to form a second electric motor assembly that is detachably mounted to the pump case so as to rotate the second control shaft around the axis line, the first electric motor assembly is mounted to the pump case so that the corresponding electric motor has a rotational axis line in parallel with the first pump shaft in a state where the electric motor is positioned on an opposite side to the second control shaft with respect to the first control shaft and is also positioned on an opposite side to the first end of the first pump shaft with respect to a virtual plane that passes through the axis lines of the first and second control shafts, and the second electric motor assembly is mounted to the pump case at a posture obtained by rotating the first electric motor assembly by 180 degrees about a virtual center line that is disposed in parallel with the first and second control shafts and is located at a center between the first and second control shafts, thereby the electric motor of the second electric motor assembly is positioned on an opposite side to the cooling fan with respect to the virtual plane.

The hydraulic actuator unit according to the present invention makes it possible to mount the first electric motor assembly to the pump case while preventing the first electric motor assembly from being interfered with a transmission mechanism transmitting rotational power from the driving power source to the first end of the first pump shaft without elongating a length of a portion of the first end of the first pump shaft that is extended outward from the pump case. The hydraulic actuator unit makes it also possible to mount the second electric motor assembly to the pump case while preventing the second electric motor assembly from being interfered with the cooling fan supported by the second end of the second pump shaft without elongating a length of a portion of the second end of the second pump shaft that is extended outward from the pump case. Accordingly, the hydraulic actuator unit could be reduced in size as a whole.

Further, in the hydraulic actuator unit according to the present invention, the first and second electric motor assemblies have the same configuration to each other. Accordingly, it is possible to enhance assembling workability and simplify inventory management thanks to common use of components.

Preferably, the hydraulic actuator unit according to the present invention further includes a pair of first spring pieces for holding the first control shaft at a neutral position around the axis line, a first engagement arm that is directly or indirectly supported by the first control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of first spring pieces, a pair of second spring pieces for holding the second control shaft at a neutral position around the axis line, and a second engagement arm that is directly or indirectly supported by the second control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of second spring pieces, wherein the electric motor cover is provided with a prevention arm that pushes the corresponding pair of spring pieces apart from each other so that the corresponding engagement arm receives no influence from the pair of spring pieces upon mounting of the electric motor cover to the pump case.

The hydraulic actuator unit with the preferable configuration makes it possible to obtain neutral-returning/neutral-holding function for returning the variable displacement mechanism to its neutral state and holding the same at the neutral state by the pair of spring pieces in the manual mode in which the electric motor assembly is detached from the pump case and the variable displacement mechanism is manually operated while effectively preventing the biasing force of the pair of spring pieces from acting on the electric motor as load in the electric mode in which the electric motor assembly is mounted to the pump case and the variable displacement mechanism is operated by the electric motor. Accordingly, it is possible to selectively realize the manual mode with the neutral-returning/neutral-holding function by the pair of spring pieces or the electric mode in which unnecessary load on the electric motor by the pair of spring pieces is prevented, only by mounting or detaching the electric motor assembly to or from the pump case.

Preferably, the pair of first spring pieces and the pair of second spring pieces are directly or indirectly mounted to the pump case so as to be positioned between the first and second control shafts.

The configuration makes it possible that the first and second spring pieces are provided without enlarging the hydraulic actuator unit.

More specifically, the hydraulic actuator unit further includes a pair of sector gears that are directly or indirectly supported by the corresponding control shafts in a relatively non-rotatable manner with respect thereto and are engaged with the corresponding electric motor output gears, the engagement arm being integrally formed with a member forming the corresponding sector gear.

More preferably, the electric motor output mechanism may have a worm shaft that is operatively connected to the output shaft of the electric motor main body, a worm wheel that is engaged with the worm shaft, an electric motor output shaft that is supported by the electric motor case in a rotatable manner about its axis line and supports the worm wheel in a relatively non-rotatable manner with respect thereto, and an electric motor output gear that is supported by the electric motor output shaft in a relatively non-rotatable manner with respect thereto.

The preferable configuration makes it possible to allow the electric motor output gear to be rotated upon rotation of the electric motor main body while preventing unintentional rotation of the electric motor output gear, that is unintentional rotation of the control shaft, at the time when the electric motor main body is in a non-operated state.

In place of or in addition to the configuration, each of the electric motors may be provided with a clutch structure that has a reverse-rotation preventing function of preventing the electric motor main body from being rotated by power applied from the electric motor output gear of the electric motor output mechanism while allowing the electric motor output gear to be rotated upon rotation of the electric motor main body.

The configuration with the clutch structure makes it also possible to prevent unintentional rotation of the electric motor output gear, that is unintentional rotation of the control shaft, at the time when the electric motor main body is in the non-operated state.

A second object of the present invention is to provide a hydraulic actuator unit including a pump case, a pump shaft that is supported by the pump case in a rotatable manner around its axis line, a hydraulic pump main body that is accommodated in the pump case in a state of being supported by the pump shaft in a relatively non-rotatable manner with respect thereto, a variable displacement mechanism that changes a displacement of the hydraulic pump main body, and a electric motor that actuates the variable displacement mechanism, the hydraulic actuator unit capable of obtaining neutral-returning/neutral-holding function for returning the variable displacement mechanism to its neutral state and holding the same at the neutral state by a pair of spring pieces in the manual mode in which the electric motor is detached and the variable displacement mechanism is manually operated while effectively preventing the biasing force of the pair of spring pieces from acting on the electric motor as load in the electric mode in which the electric motor is mounted to the pump case and the variable displacement mechanism is operated by the electric motor.

In order to achieve the second object, the present invention provides a hydraulic actuator unit including a pump case, a pump shaft that is supported by the pump case in a rotatable manner around its axis line, a hydraulic pump main body that is accommodated in the pump case in a state of being supported by the pump shaft in a relatively non-rotatable manner with respect thereto, a variable displacement mechanism that changes a displacement of the hydraulic pump main body, and a electric motor that actuates the variable displacement mechanism, the hydraulic actuator unit further including an electric cover to which the electric motor is mounted and which is detachably connected to the pump case with the electric motor being mounted thereto, a motor transmission mechanism that operatively connects an electric motor output gear of the electric motor to a control shaft of the variable displacement mechanism upon mounting of an electric motor assembly, which is formed by the electric motor and the electric motor cover, to the pump case, a pair of spring pieces that hold the control shaft at a neutral position around its axis line, and an engagement arm that is directly or indirectly supported by the control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of spring pieces, wherein the electric motor cover is provided with a prevention arm that pushes the pair of spring pieces apart from each other so that the engagement arm receives no influence from the pair of spring pieces upon mounting of the electric motor cover to the pump case.

The hydraulic actuator unit according to the present invention makes it possible to obtain neutral-returning/neutral-holding function for returning the variable displacement mechanism to its neutral state and holding the same at the neutral state by the pair of spring pieces in the manual mode in which the electric motor assembly is detached and the variable displacement mechanism is manually operated while effectively preventing the biasing force of the pair of spring pieces from acting on the electric motor as load in the electric mode in which the electric motor assembly is mounted to the pump case and the variable displacement mechanism is operated by the electric motor.

In one embodiment, the pump shaft includes first and second pump shafts that are arranged in parallel with each other and are operatively connected to each other, the hydraulic pump main body includes first and second hydraulic pump main bodies that are supported by the first and second pump shafts respectively in a relatively non-rotatable manner with respect thereto, the variable displacement mechanism includes first and second variable displacement mechanisms that change displacements of the first and second hydraulic pump main bodies, respectively, the electric motor includes first and second electric motors that have the same configuration to each other and actuate the first and second variable displacement mechanisms, respectively, the electric motor cover includes first and second electric motor covers that have the same configuration to each other and form first and second electric motor assemblies in cooperation with the first and second electric motors, respectively, the motor transmission mechanism includes first and second motor transmission mechanisms that have the same configuration to each other and operatively connect the electric motor output gears of the corresponding electric motors to the corresponding control shafts, respectively, the pair of spring pieces includes a pair of first spring pieces that hold a first control shaft of the first variable displacement mechanism at a neutral position around its axis line and a pair of second spring pieces that hold a second control shaft of the second variable displacement mechanism at a neutral position around its axis line, the engagement arm includes a first engagement arm that is directly or indirectly supported by the first control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of first spring pieces and a second engagement arm that is directly or indirectly supported by the second control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of second spring pieces, and the prevention arm includes a first prevention arm that is provided at the first electric motor cover so as to push the pair of first spring pieces apart from each other so that the first engagement arm receives no influence from the pair of first spring pieces upon mounting of the first electric motor cover to the pump case and a second prevention arm that is provided at the second electric motor cover so as to push the pair of second spring pieces apart from each other so that the second engagement arm receives no influence from the pair of second spring pieces upon mounting of the second electric motor cover to the pump case, wherein the first and second control shafts are supported by the pump case in a rotatable manner around the respective axis lines in a state where they are parallel to each other and their ends that are operatively connected to the corresponding electric motors face in the same direction to each other, wherein the first electric motor cover supports the first electric motor so as to be positioned on an opposite side to the second control shaft with respect to the first control shaft, wherein the second electric motor cover supports the second electric motor so as to be positioned on an opposite side to the first control shaft with respect to the second control shaft, and wherein the pair of first spring pieces and the pair of second spring pieces are positioned between the first and second control shafts.

The configuration makes it possible to reduce a size of the hydraulic actuator unit with the pair of first spring pieces and the pair of second spring pieces as much as possible.

Preferably, each of the first and second electric motors has an electric motor main body that is controlled and driven based on an external electric signal, an electric motor output mechanism that is operatively connected to an output shaft of the electric motor main body, and an electric motor case that supports the electric motor main body and the electric motor output mechanism, wherein the electric motor output mechanism has a worm shaft that is operatively connected to the output shaft of the electric motor main body, a worm wheel that is engaged with the worm shaft, an electric motor output shaft that is supported by the electric motor case in a rotatable manner about its axis line and supports the worm wheel in a relatively non-rotatable manner with respect thereto, and an electric motor output gear that is supported by the electric motor output shaft in a relatively non-rotatable manner with respect thereto and is operatively connected to the motor transmission mechanism.

The preferable configuration makes it possible to allow the electric motor output gear to be rotated upon rotation of the electric motor main body while preventing unintentional rotation of the electric motor output gear, that is unintentional rotation of the control shaft, at the time when the electric motor main body is in a non-operated state.

In place of or in addition to the configuration, each of the first and second electric motors may have an electric motor main body that is controlled and driven based on an external electric signal, an electric motor output mechanism that is operatively connected to an output shaft of the electric motor main body, an electric motor case that supports the electric motor main body and the electric motor output mechanism, and a clutch structure that has a reverse-rotation preventing function of preventing the electric motor main body from being rotated by power applied from the electric motor output gear of the electric motor output mechanism while allowing the electric motor output gear to be rotated in accordance with rotation of the electric motor main body.

The provision of the clutch structure makes it also possible to prevent unintentional rotation of the electric motor output gear, that is unintentional rotation of the control shaft, at the time when the electric motor main body is in a non-operated state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a hydraulic actuator unit according to a first embodiment of the present invention.

FIG. 2 is a cross sectional view taken along line II-II inFIG. 1.

FIG. 3 is a cross sectional view taken along line III-III inFIG. 2.

FIG. 4 is an exploded perspective view of the hydraulic actuator unit taken along line IV-IV inFIG. 2.

FIG. 5 is a cross sectional view taken along line V-V inFIG. 1.

FIGS. 6A to 6C are cross sectional views taken along line VI-VI inFIG. 5.

FIGS. 7A and 7B are cross sectional views taken along line VII-VII inFIG. 1.FIG. 7A shows a state where an electric motor cover of the hydraulic actuator unit is being attached a pump case, andFIG. 7B shows a state where the electric motor cover has been attached to the pump case.

FIG. 8 is a cross sectional view taken along line III-III inFIG. 2 with the electric motor covers being detached.

FIG. 9 is a schematic view of an operation rod that may be used in a manual mode.

FIG. 10 is an end view of a hydraulic actuator unit according to a modified example of the first embodiment.

FIG. 11 is a cross sectional view taken along line XI-XI inFIG. 10.

FIG. 12A is a side view of a first example of a working vehicle to which the hydraulic actuator unit according to the present invention could be applied.

FIG. 12B is a schematic view of an operation unit included in the working vehicle according to the first example.

FIG. 13 is a system block diagram of a control unit included in the working vehicle according to the first example.

FIG. 14 is a side view of a second example of the working vehicle to which the hydraulic actuator unit according to the present invention could be applied.

FIGS. 15A and 15B are schematic front and side views of an operation unit included in the working vehicle according to the second example, respectively.

FIG. 16A is a side view of a third example of the working vehicle to which the hydraulic actuator unit according to the present invention could be applied.

FIG. 16B is a perspective view of an operation unit included in the working vehicle according to the third example.

FIG. 17 is a side view of the working vehicle according to the third example in a state of being changed to a manual mode.

FIGS. 18A and 18B are front and side views of an operation unit of a fourth example of the working vehicle to which the hydraulic actuator unit according to the present invention could be applied, respectively.

FIGS. 19A and 19B are plan and side views of a fifth example of the working vehicle to which the hydraulic actuator unit according to the present invention could be applied, respectively.

FIGS. 20A and 20B are plan and side views of a sixth example of the working vehicle to which the hydraulic actuator unit according to the present invention could be applied, respectively.

FIG. 21 is a side view of a seventh example of the working vehicle to which the hydraulic actuator unit according to the present invention could be applied.

FIG. 22 is a side view of an eighth example of the working vehicle to which the hydraulic actuator unit according to the present invention could be applied.

FIG. 23 is a side view of a ninth example of the working vehicle to which the hydraulic actuator unit according to the present invention could be applied.

FIG. 24 is a flowchart of a control program of the control device.

FIG. 25 is a flowchart of an engine start program included in the control program.

FIG. 26 is a flowchart of an error detection program included in the control program.

FIG. 27 is a plan view of a hydraulic actuator unit according to a second embodiment of the present invention.

FIG. 28 is a cross sectional view taken along line XXVIII-XXVIII inFIG. 27.

FIG. 29 is a cross sectional view taken along line XXIX-XXIX inFIG. 27.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Hereinafter, a preferred embodiment of a hydraulic actuator unit according to the present application will be explained with reference to the accompanying drawings.

FIG. 1 is a front view of ahydraulic actuator unit1A according to the present embodiment.

FIGS. 2 and 3 are cross sectional views taken along line II-II inFIG. 1 and line III-III inFIG. 2, respectively.

Further,FIG. 4 is an exploded perspective view of thehydraulic actuator unit1A taken along line IV-IV inFIG. 2.

Thehydraulic actuator unit1A includes a rotary shaft, a hydraulic actuator that is supported by the rotary shaft in a relatively non-rotatable manner with respect thereto, avariable displacement mechanism40 that changes the displacement of the hydraulic actuator, and anelectric motor50 that actuates thevariable displacement mechanism40.

As shown inFIGS. 1 to 3, thehydraulic actuator unit1A according to the present embodiment is formed as a hydraulic pump unit that includes first and second hydraulic pump main bodies10(1) and10(2) each functioning as the hydraulic actuator.

Specifically, as shown inFIGS. 1 to 4, the hydraulic actuator unit according to the present embodiment includes first and second pump shafts20(1) and20(2) each of which functions as the rotary shaft and that are operatively connected to a driving power source (not shown) in a state of being disposed in parallel to each other, the first and second hydraulic pump main bodies10(1) and10(2) that are supported by the first and second pump shafts20(1) and20(2) in a relatively non-rotatable manner, respectively, and apump case30 that accommodates the first and second hydraulic pump main bodies10(1) and10(2) and also supports the first and second pump shafts20(1) and20(2) in a rotatable manner around respective axis lines.

Thehydraulic actuator unit1A is configured such that the displacements of the first and second hydraulic pump main bodies10(1) and10(2) can be changed independently from each other.

More specifically, thehydraulic actuator unit1A includes a pair ofvariable displacement mechanisms40 that are each configured identically with thevariable displacement mechanism40 described earlier and change the displacements of the first and second hydraulic pump main bodies10(1) and10(2), respectively, and a pair ofelectric motors50 that are each configured identically with theelectric motor50 described earlier and actuate the pair ofvariable displacement mechanisms40, respectively.

In the present specification, where appropriate, thevariable displacement mechanisms40 will be distinctively referred to as a first variable displacement mechanism40(1) and a second variable displacement mechanism40(2), which change the displacements of the first hydraulic pump main body10(1) and the second hydraulic pump main body10(2), respectively.

Moreover, where appropriate in the present specification, theelectric motors50 will be distinctively referred to as a first electric motor50(1) and a second electric motor50(2), which actuate the first variable displacement mechanism40(1) and the second variable displacement mechanism40(2), respectively.

In the present embodiment, as shown inFIGS. 1 and 3, one pump shaft (for example, the first pump shaft20(1)) of the first and second pump shafts20(1) and20(2) has a first end extending outward from thepump case30 to form an input end capable of being operatively connected to the driving power source.

The other one pump shaft (for example, the second pump shaft20(2)) of the first and second pump shafts20(1) and20(2) is operatively connected to the one pump shaft trough a power transmission gear mechanism (not shown) accommodated in thepump case30.

Preferably, at least one of a second end of the one pump shaft that is opposite from the first end and a end of the other one pump shaft that is positioned on the same side as the second end of the one pump shaft is extended outward from thepump case30 to form an outward-extended end. The hydraulic actuator unit A is provided with acharge pump unit90 driven by the outer-extended end.

In the present embodiment, as shown inFIG. 3, the first pump shaft20(1) functioning as the one pump shaft has the second end that is extended outward from thepump case30, and the second pump shaft20(2) functioning as the other one pump shaft has the end that is positioned on the same side as the second end of the firs pump shaft20(1) and is extended outward from thepump case30 to form the outward-extended end, so that the second end of the first pump shaft20(1) drives thecharge pump90 and the outward-extended end of the second pump shaft20(2) drive a coolingfan95.

As explained above, the hydraulic actuator unit according to the present embodiment is in form of the hydraulic pump unit including the first and second hydraulic pump main bodies10(1) and10(2), and is configured so as to suction and discharge operational fluid from/to first and second motor main bodies (not shown) trough a pair of first HST lines (not shown) and a pair of second HST lines (not shown), respectively.

Specifically, thepump case30 is formed with a pair of first pump-side operational fluid passages (not shown) and a pair of second pump-side operational fluid passages (not shown) that form a part of the pair of first HST lines and a part of the pair of second HST lines, respectively.

The pair of first pump-side operational fluid passages have first ends fluidly connected to the first hydraulic pump main body10(1) and second ends opened to an outer surface to form a pair of first pump-side operational fluid ports (not shown).

The pair of second pump-side operational fluid passages have first ends fluidly connected to the second hydraulic pump main body10(2) and second ends opened to the outer surface to form a pair of second pump-side operational fluid ports (not shown).

A pair of first external conduits (not shown) forming a part of the first HST lines are fluidly connected to the pair of first pump-side operational fluid passages, respectively. That is, the first hydraulic pump main body10(1) is fluidly connected to the cooperating hydraulic motor main body (for example, the first hydraulic motor main body operatively driving one of the pair of driving wheels in the working vehicle) through the pair of first pump-side operational fluid passages and the pair of first external conduits.

Similarly, a pair of second external conduits (not shown) forming a part of the second HST lines are fluidly connected to the pair of second pump-side operational fluid passages, respectively. That is, the second hydraulic pump main body10(2) is fluidly connected to the cooperating hydraulic motor main body (for example, the second hydraulic motor main body operatively driving the other one of the pair of driving wheels in the working vehicle) through the pair of second pump-side operational fluid passages and the pair of second external conduits.

In the present embodiment, as shown inFIGS. 1 to 3, thepump case30 includes apump case body31 and aport block32 that are detachably connected to each other in the axis lines of the first and second pump shafts20(1) and20(2).

Thepump case body31 has a hollow shape including anend wall31athat is positioned on one side in the axis line direction of the first and second pump shafts20(1) and20(2) and is extended in a direction orthogonal to the first and second pump shafts20(1) and20(2), aperipheral wall31bthat is extended toward the other side in the axis line direction of the first and second pump shafts20(1) and20(2) from a peripheral edge of theend wall31a, and an opening (not shown) that is provided at the other side of theperipheral wall31bin the axis line direction of the first and second pump shafts20(1) and20(2) and has a size allowing the first and second hydraulic pump main bodies10(1) and10(2) to be passed therethrough.

Theport block32 is detachably connected to thepump case body31 so as to close the opening to form a pump space for accommodating the first and second hydraulic pump main bodies10(1) and10(2).

That is, the first and second hydraulic pump main bodies10(1) and10(2) are accommodated in the pump space defined by thepump case body31 and theport block32 in a state of being supported by the corresponding pump shafts20(1) and20(2) in a relatively non-rotatable manner with respect thereto.

The first and second hydraulic pump main bodies10(1) and10(2) are configured identically with each other. Thus, where appropriate in the following description, the first and second hydraulic pump main bodies10(1) and10(2) will be each referred to simply as the hydraulic pumpmain body10.

The hydraulic pumpmain bodies10 may be variously embodied such as of the axial piston type or of the radial piston type, as far as each of which is capable of supplying/exhausting hydraulic fluid in accordance with rotation of corresponding one of the pump shafts20(1) and20(2).

In the present embodiment, the hydraulic pump main body is of an axial piston type.

Specifically, the hydraulic pump main body includes a cylinder block (not shown) supported by the corresponding pump shaft20(1) or20(2), and a plurality of pistons (not shown) accommodated in the cylinder block in a relatively non-rotatable manner around the corresponding pump shaft and in a relatively movable manner along the axis line direction of the corresponding pump shaft with respect to the cylinder block.

Each of thevariable displacement mechanisms40 is capable of changing, in response to external operation, the displacement of corresponding one of the hydraulic pumpmain bodies10, namely, the volume and the direction of hydraulic fluid to be sucked/discharged by the corresponding hydraulic pumpmain body10.

More specifically, thevariable displacement mechanism40 is configured to be brought into a neutral state, a normal-rotation output state, and a reverse-rotation output state. In the neutral state, the suction/discharge amount of the corresponding hydraulic pumpmain body10 is made substantially equal to zero to cause the output from the cooperating hydraulic motor main body to be zero. In the normal-rotation output state, the corresponding hydraulic pumpmain body10 sucks hydraulic fluid from a first one of the corresponding HST lines and discharges to a second one of the HST lines so as to rotate the hydraulic motor main body in the normal-rotation direction. In the reverse-rotation output state, the corresponding hydraulic pumpmain body10 sucks hydraulic fluid from the second one of the HST lines and discharges to the first one of the HST lines so as to rotate the hydraulic motor main body in the reverse-rotation direction.

As described above, in the present embodiment, the hydraulic pump main body is of the axial piston type.

Thus, as shown inFIGS. 1 to 4, in the present embodiment, thevariable displacement mechanisms40 each include a movable swash plate42 (42(1) and42(2), respectively) which is capable of changing the reciprocation range of the pistons in the corresponding hydraulic pumpmain body10 in accordance with the slanting position thereof around the swing axis line, and acontrol shaft41 that is supported by thepump case30 in a rotatable manner around its axis line so as to cause themovable swash plate42 to be slanted in accordance with rotation of thecontrol shaft41 around the axis line.

More specifically, each of themovable swash plates42 can be slanted between a nornal-rotation-outputting-side maximum slanting position on one side around the swing axis line and a reverse-rotation-outputting-side maximum slanting position on the other side around the swing axis line.

Each of thecontrol shafts41 is supported by thepump case30 in a rotatable manner around its axis line, with a first end being located in thepump case30 so as to be operatively connected with corresponding one of themovable swash plates42 and asecond end41bbeing extended outward from thepump case30 so as to be externally operated.

As shown inFIGS. 1 to 4, in the present embodiment, thecontrol shafts41 of the pair ofvariable displacement mechanisms40 are supported by thepump case30 so as to be parallel to each other with the second ends41bbeing extended outward from an identical side surface of thepump case30.

As shown inFIG. 1, theelectric motors50 each have an electric motormain body51 that is controlled and driven based on an external electric signal, an electricmotor output mechanism52 that is operatively connected to anoutput shaft51aof the electric motormain body51, and anelectric motor case53 that accommodates the electric motormain body51 and the electricmotor output mechanism52.

As shown inFIGS. 1 to 4, each of the electricmotor output mechanisms52 is operatively connected to corresponding one of thecontrol shafts41 via amotor transmission mechanism60.

In other words, thehydraulic actuator unit1A according to the present embodiment includes, in addition to the components recited above, a pair of themotor transmission mechanisms60 each of which transmits, to corresponding one of the pair ofvariable displacement mechanisms40, rotational power generated by corresponding one of the pair ofelectric motors50.

More specifically, as shown inFIGS. 1 to 4, the electricmotor output mechanism52 has aworm shaft52athat is operatively connected to theoutput shaft51aof the electric motormain body51, aworm wheel52bthat is engaged with theworm shaft52a, an electricmotor output shaft52cthat is supported by theelectric motor case53 in a rotatable manner about its axis line and supports theworm wheel52bin a relatively non-rotatable manner with respect thereto, and an electricmotor output gear52dthat is supported by the electricmotor output shaft52cin a relatively non-rotatable manner with respect thereto.

The electricmotor output gear52dpreferably has a radius smaller than that of theworm wheel52b.

Each of themotor transmission mechanisms60 includes asector gear61 that is engaged with the electricmotor output gear52d, and anoperation shaft62 that supports thesector gear61 in a relatively non-rotatable manner with respect thereto. Theoperation shaft62 is connected to corresponding one of thecontrol shafts41 so as to be relatively non-rotatable around its axis line with respect thereto.

In the present embodiment, theoperation shaft62 has a hollow portion62athat allows thesecond end41bof thecorresponding control shaft41 to be inserted thereinto. Theoperation shaft62 is connected by means of a bolt to thecontrol shaft41 so as to be relatively non-rotatable with respect thereto in a state where thesecond end41bof thecontrol shaft41 is inserted into the hollow portion62a.

Thehydraulic actuator unit1A according to the present embodiment further includes a pair of electric motor covers70 each of which allows corresponding one of theelectric motors50 to be detachably mounted and is detachably connected directly or indirectly to thepump case30 so as to cover at least the upper portion (a side facing in a direction opposite from the pump case30) of corresponding one of themotor transmission mechanisms60 in a state where the correspondingelectric motor50 is mounted thereto.

As shown inFIG. 4, in the present embodiment, the electric motor covers70 are detachably connected to abase plate80 that is detachably connected to thepump case30.

More specifically, as shown inFIGS. 2 and 4, thehydraulic actuator unit1A according to the present embodiment includes thebase plate80 that is detachably connected to one of the side surfaces of thepump case30 from which the second ends41bof the pairedcontrol shafts41 are extended outward.

As shown inFIG. 4, thebase plate80 is provided withopenings81 that allow the second ends41bof the pair ofcontrol shafts41 to be inserted therethrough. Thebase plate80 is detachably connected to the relevant side surface of thepump case30 by means of afastening member85 such as a bolt with the second ends41bof the pair ofcontrol shafts41 being inserted through theopenings81, respectively.

As shown inFIGS. 2 and 4, theoperation shaft62 is placed on the upper surface (the surface on a side opposite from the pump case30) of thebase plate80 with thesecond end41bof thecorresponding control shaft41 being inserted into the hollow portion62a.

Theelectric motor case53 of each of theelectric motors50 is detachably connected to corresponding one of the electric motor covers70 by means of afastening member55 such as a bolt. Theelectric motor50 and theelectric motor cover70 thus integrally form an electric motor assembly that is attached directly or indirectly to thepump case30.

Each of the electric motor covers70 is detachably connected to thebase plate80 by means offastening members79 such as bolts, so that the electric motor assembly is connected to thepump case30.

More specifically, as shown inFIG. 4, the electric motor covers70 each have a motor transmissionmechanism cover portion71 that covers the upper portion (the end surface of theoperation shaft62 not facing the pump case30) of theoperation shaft62 of corresponding one of themotor transmission mechanisms60, an electricmotor mount portion72 to which corresponding one of theelectric motors50 is connected, and aconnection portion73 that is fixed to a mount portion (thebase plate80 in the present embodiment).

In the present embodiment, each of the electric motor covers70 has aside wall portion74 that has a proximal end being placed onto the mount portion and a distal end supporting the motor transmissionmechanism cover portion71.

Theside wall portion74 surrounds the side portion of theoperation shaft62 in such a manner as to allow the electricmotor output gear52dand thesector gear61 to be engaged with each other in the state where theelectric motor cover70 mounted with theelectric motor50 is directly or indirectly attached to thepump case30.

In other words, theside wall portion74 partially surrounds theoperation shaft62 so as to open at least a side of the periphery of theoperation shaft62 on which thesector gear61 is positioned.

In the present embodiment, theside wall portion74 has a pair of side walls74athat are located so as to sandwich theoperation shaft62 therebetween.

The electricmotor mount portion72 is extended from the motor transmissionmechanism cover portion71 toward a side on which thesector gear61 is located with theoperation shaft62 as a reference, and is configured so that a lower surface facing thepump case30 serves as an electric motor mount surface.

More specifically, in the present embodiment, each of theelectric motors50 is mounted on the lower surface of the corresponding electricmotor mount portion72 to thereby configure the electric motor assembly, which is attached directly or indirectly to thepump case30 so that the electricmotor output gear52dis engaged with the correspondingsector gear61.

As shown inFIGS. 1,2, and4, thehydraulic actuator unit1A according to the present embodiment includes a pair of speed change actuating-side sensors210 that detect actuation states of the pair ofvariable displacement mechanisms40, respectively.

In the present embodiment, each of the speed change actuating-side sensors210 is configured to detect the rotation position around the respective axis line of corresponding one of theoperation shafts62.

In the present specification, where appropriate, the speed change actuating-side sensors210 which detect the actuation states of the first variable displacement mechanism40(1) and the second variable displacement mechanism40(2) will be referred to as a first speed change actuating-side sensor210(1) and a second speed change actuating-side sensor210(2), respectively.

More specifically, as shown inFIG. 4, theoperation shaft62 has a detectedportion62bat an end on a side opposite from an end connected with thecontrol shaft41.

Each of the electric motor covers70 has an opening71ain the motor transmissionmechanism cover portion71 at a portion to face the detectedportion62b. Each of the speed change actuating-side sensors210 is attached to corresponding one of the electric motor covers70 so as to detect an angle of rotation of the detectedportion62bvia the opening71a.

As shown inFIG. 1, each of theelectric motors50 is preferably provided with aclutch structure100 that has a reverse-rotation preventing function of preventing theworm shaft52afrom being rotated around the axis line by power applied from corresponding one of the variable displacement mechanisms while allowing theworm shaft52ato be rotated around the axis line in accordance with rotation of the electric motormain body51.

Provision of theclutch structure100 effectively prevents themovable swash plate42 from unintentionally slanting from a set slanting position while allowing themovable swash plate42 to be slanted by the electric motormain body51.

FIG. 5 is a cross sectional view of theclutch structure100 taken along line V-V indicated inFIG. 1.

FIGS. 6A to 6C are cross sectional views of theclutch structure100 taken along line VI-VI indicated inFIG. 5.

As shown inFIGS. 5 and 6A to6C, theclutch structure100 includes a driving-side arm101 that is provided at an distal end of theoutput shaft51aof the electric motormain body51 so as to extend radially outward, acollar member110 that surrounds the driving-side arm101, a driven-side arm102 that is provided at the end of theworm shaft52acloser to theoutput shaft51aso as to extended radially outward, and acontact member105 that is disposed between the driven-side arm102 and thecollar member110 with respect to a radial direction with the axis line of theoutput shaft51aand theworm shaft52abeing as a reference.

The driving-side arm101 hasside surfaces101afacing in a circumferential direction with the axis line of theoutput shaft51abeing as a reference, and the side surfaces101aare configured so as to press, in the circumferential direction, side surfaces102aand105aof the driven-side arm102 and thecontact member105 that face in the circumferential direction.

As shown inFIGS. 6A to 6C, the driven-side arm102 has anouter end surface102bthat faces radially outward, theouter end surface102bbeing substantially perpendicular to a virtual line IL connecting a circumferential center of theouter end surface102band an axis line CL of theoutput shaft51aand theworm shaft52awhen seen along the axis line CL.

Theclutch structure100 thus configured is actuated as follows.

When the correspondingelectric motor50 receives from acontrol unit500 to be described below, which is provided in a working vehicle adopting thehydraulic actuator unit1 A, a control signal for axially rotating the electric motormain body51 in one direction (normal rotation for allowing the working vehicle to travel forward, for example) around the axis line or in the other one direction (reverse rotation for allowing the working vehicle to travel rearward, for example), the electric motormain body51 is rotated in one of the directions (hereinafter, referred to as a first direction D1) around the axis line according to the control signal (seeFIG. 6A) so that the driving-side arm101 presses both the driven-side arm102 and thecontact member105 into the first direction D1. Accordingly, theworm shaft52ais rotated in a direction d1 identical with the first direction D1 (seeFIG. 6B) so that themovable swash plate42 is slanted into a direction corresponding to the first direction D1.

The hydraulic pressure of the operational fluid that the hydraulic actuator (the hydraulic pumpmain body10 in the present embodiment) suctions and discharges may function as power applied to themovable swash plate42 for slanting the same. Further, in accordance with needs, thehydraulic actuator unit1A may further includeneutral springs120 that bias themovable swash plates42 toward the neutral positions, respectively.

Therefore, when theelectric motor50 is in non-actuation state, themovable swash plate42 is slightly slanted toward the neutral position against the inertial force of theelectric motor50.

In accordance with this slanting, as shown inFIG. 6C, theworm shaft52athat is operatively connected to themovable swash plate42 is rotated in a second direction d2 corresponding to the direction toward the neutral position, while the position of the freely providedcontact member105 being unchanged.

As described above, each of the outer end surfaces102bof the driven-side arm102 is substantially perpendicular to the virtual line IL connecting the circumferential center of theouter end surface102band the axis CL of theworm shaft52a. Therefore, rotation of the driven-side arm102 into the second direction d2 causes thecontact member105 to be pressed to the inner circumferential surface of thecollar member110, so that theworm shaft52ais in a locked state incapable of being rotated (seeFIG. 6C).

As a result, it is possible to effectively prevent themovable swash plate42 from unintentionally slanting from a predetermined slanting position after theelectric motor50 locates themovable swash plate42 at the predetermined slanting position.

Thehydraulic actuator unit1A according to the present embodiment further has a configuration as described below so as to be easily switched between an electric mode of actuating thevariable displacement mechanisms40 with use of theelectric motors50 and a manual mode of manually actuating thevariable displacement mechanisms40.

More specifically, as shown inFIGS. 1,3, and4, thehydraulic actuator unit1A includes theneutral springs120 that bias thevariable displacement mechanisms40 toward the neutral positions, respectively.

As described earlier, thehydraulic actuator unit1A according to the present embodiment includes the pair ofvariable displacement mechanisms40. Accordingly, thehydraulic actuator unit1A includes a pair of theneutral springs120 that bias the pair ofvariable displacement mechanisms40 toward the neutral positions, respectively.

Although being useful in the manual mode of manually operating thevariable displacement mechanisms40, theseneutral springs120 are not required in the electric mode of operating thevariable displacement mechanisms40 with use of theelectric motors50.

More specifically, in the electric mode, the position control of each of thevariable displacement mechanisms40 is performed based on an electric control signal that is received by corresponding one of theelectric motors50. In such electric mode, the influence of theneutral spring120 increases the load applied to theelectric motor50 and thus increases the power consumed by theelectric motor50.

Moreover, theneutral spring120 generates the biasing power that is gradually increased as thevariable displacement mechanism40 is shifted from the neutral position toward the actuation position (in the present embodiment, as themovable swash plate42 is gradually slanted from the neutral position toward the maximum slanting position). Accordingly, if theneutral spring120 influences thevariable displacement mechanism40 in the electric mode, the response of thevariable displacement mechanism40 to be actuated and controlled by theelectric motor50 will be varied in accordance with the actuation state of thevariable displacement mechanism40.

In view of the above, thehydraulic actuator unit1A according to the present embodiment is configured so as to inhibit theneutral springs120 from influencing thevariable displacement mechanisms40 in the electric mode while allowing theneutral springs120 to influence thevariable displacement mechanisms40 in the manual mode

More specifically, as shown inFIGS. 3 and 4, thehydraulic actuator unit1A includesengagement arms65 that are supported respectively by theoperation shafts62 in a relatively non-rotatable manner with respect thereto.

In the present embodiment, theengagement arms65 are each formed integrally with corresponding one of the sector gears61.

As already described, theoperation shafts62 are operatively connected to thevariable displacement mechanisms40, respectively. Thus, theengagement arms65 swing about the axis line of theoperation shafts62 in accordance with the actuation states of thevariable displacement mechanisms40, respectively.

Specifically, when thevariable displacement mechanism40 is in the neutral state, theengagement arm65 is located at the neutral position around the axis line of theoperation shaft62.

In a case where thevariable displacement mechanism40 is shifted from the neutral state into the normal-rotation output state, the correspondingengagement arm65 is turned from the neutral position into a first direction about the axis line of theoperation shaft62. When thevariable displacement mechanism40 is brought into the maximum normal-rotation output state (in the present embodiment, when themovable swash plate42 is located at the normal rotation maximum slanting position), theengagement arm65 is turned around the axis line from the neutral position fully into the first direction to reach a normal-rotation maximum position.

In a case where thevariable displacement mechanism40 is shifted from the neutral state into the reverse-rotation output state, the correspondingengagement arm65 is turned from the neutral position into a second direction about the axis line of theoperation shaft62. When thevariable displacement mechanism40 is brought into the maximum reverse-rotation output state (in the present embodiment, when themovable swash plate42 is located at the reverse rotation maximum slanting position), theengagement arm65 is turned around the axis line from the neutral position fully into the second direction to reach a reverse-rotation maximum position.

In summary, theengagement arm65 is rotated about the axis line of thecorresponding operation shaft62 within a rotational range between the normal-rotation maximum position and the reverse-rotation maximum position in accordance with the actuation state of the correspondingvariable displacement mechanism40.

As shown inFIG. 4, theneutral spring120 has a pair ofspring pieces121 that can sandwich theengagement arm65 of corresponding one of theoperation shafts62.

Theneutral spring120 is attached directly or indirectly to thepump case30 at a position where the pair ofspring pieces121 holds thecorresponding engagement arm65 at the neutral position.

In the present embodiment, as shown inFIG. 4, theneutral spring120 is detachably fixed to thebase plate80.

Further, as shown inFIG. 4, theelectric motor cover70 is provided with aprevention arm75 that is inserted between the pair ofspring pieces121 of the correspondingneutral spring120 so as to push the pair ofspring pieces121 apart from each other when theelectric motor cover70 is attached directly or indirectly to thepump case30.

Theprevention arm75 is extended from the motor transmissionmechanism cover portion71 toward a side on which theengagement arm65 is located.

Theside wall portion74 is configured so as to open a side of the periphery of theoperation shaft62 on which theengagement arm65 is located.

FIGS. 7A and 7B are cross sectional views taken along line VII-VII indicated inFIG. 1.

FIG. 7A shows a state where theelectric motor cover70 is being attached the pump case30 (thebase plate80 in the present embodiment).FIG. 7B shows a state where theelectric motor cover70 has been attached to thepump case30.

FIGS. 7A and 7B also show arotational range66 in which theengagement arm65 could be rotated.

As shown inFIG. 7B, in the state where theelectric motor cover70 has been attached to thepump case30, theprevention arm75 pushes the pair ofspring pieces121 of the correspondingneutral spring120 apart from each other so that theengagement arm65 is allowed to be freely rotated within therotational range66 with no influence of the pair ofspring pieces121.

FIG. 8 is a cross sectional view taken along line III-III shown inFIG. 2 with the electric motor covers70 being detached.

To the contrary, when the electric motor covers70 are detached from thepump case30, as shown inFIG. 8, theneutral spring120 holds corresponding one of theengagement arms65 at the neutral position.

Thehydraulic actuator unit1A configured as described above makes it possible to prevent each of theneutral springs120 from influencing corresponding one of theengagement arms65 in the electric mode where the electric motor assembly configured by theelectric motor50 and theelectric motor cover70 being connected with each other are attached to thepump case30. Further, thehydraulic actuator unit1A makes it possible to hold each of theengagement arms65 at the neutral position by corresponding one of theneutral springs120 in the manual mode where the electric motor assembly is detached from thepump case30.

As shown inFIGS. 4,7A, and7B, free end portions of the pair ofspring pieces121 of theneutral spring120 are preferably formed to be gradually distant from each other as a distance to the free ends is reduced.

The configuration makes it possible to cause the pair ofspring pieces121 to be smoothly pushed apart from each other by theprevention arm75 upon attaching theelectric motor cover70 to thepump case30.

In the present embodiment, as shown inFIGS. 7A and 7B, the pair ofspring pieces121 each have a proximal end121athat is fixed directly or indirectly to thepump case30, anintermediate portion121bthat extends from the proximal end121ain a direction away from thepump case30, and thefree end121cthat extends from theintermediate portion121bin the direction away from thepump case30. The pair ofspring pieces121 are configured so as to sandwich corresponding one of theengagement arms65 atintermediate portions121b.

As shown inFIG. 8, a free end of theengagement arm65 is preferably has a curved shape where it is most distant from the axis line of theoperation shaft62 at a circumferential center with the axis line of theoperation shaft62 as a reference and is gradually closer to the axis line as it is away from the circumferential center into one side and the other side in the circumferential direction around the axis line.

The preferable configuration allows theengagement arm65 to be smoothly rotated within therotational range66 while being sandwiched between the pair ofspring pieces121 in the manual mode.

Preferably, thehydraulic actuator unit1A may further include a structure for assisting rotation of theoperation shaft62 in accordance with manual operation.

As shown inFIGS. 4 and 8, in the present embodiment, thesector gear61, which is supported by thecorresponding operation shaft62 in a relatively non-rotatable manner with respect thereto, is provided withengagement holes61a. In the manual mode, theoperation shaft62 can be manually rotated around the axis line easily with use of, for example, anoperation rod130 shown inFIG. 9.

Theoperation rod130 has agrip portion131 at the proximal end, anengagement portion133 at the distal end, and arod portion132 that connects thegrip portion131 and theengagement portion133. Theengagement portion133 is provided withengagement projections135 that can be engaged in the engagement holes61a, respectively.

In theoperation rod130 shown inFIG. 9, theengagement projections135 include a first engagement projection135aprovided with an outer screw and asecond engagement projection135bprovided with no outer screw.

FIG. 9 also shows anut136 that is screwed to the first engagement projection135aafter the first engagement projection135ahas been inserted into corresponding one of the engagement holes61a.

Thehydraulic actuator unit1A according to the present embodiment is formed as a dual hydraulic pump unit having the first and second hydraulic pump main bodies10(1) and10(2) disposed in parallel with each other, wherein thecontrol shafts41 which change the suction/discharge amounts and the suction/discharge directions of the hydraulic fluid of the first and second hydraulic pump main bodies10(1) and10(2), respectively, are extended outward from the identical side surface of thepump case30.

In thehydraulic actuator unit1A thus configured, as shown inFIGS. 1 to 3, the first electric motor50(1) operatively acting on the control shaft41 (hereinafter, referred to as a first control shaft41(1) where appropriate) of the first variable displacement mechanism40(1) is disposed on a side of the first control shaft41(1) that is opposite from the control shaft41 (hereinafter, referred to as a second control shaft41(2) where appropriate) of the second variable displacement mechanism40(2) so that the first control shaft41(1) is interposed between the first electric motor50(1) and the second control shaft41(2). The second electric motor50(2) operatively acting on the second control shaft41(2) is disposed on a side of the second control shaft41(2) that is opposite from the first control shaft41(1) so that the second control shaft41(2) is interposed between the second electric motor50(2) and the first control shaft41(1).

This preferable configuration realizes reduction in size of the entirehydraulic actuator unit1A that is inclusive of the first and second electric motors50(1) and50(2).

As shown inFIGS. 1 to 4, in theelectric motors50 adopted in the present embodiment, theoutput shaft51aof the electric motormain body51 and theworm shaft52aare disposed coaxially with each other, and theworm wheel52bis engaged with theworm shaft52ain a state where the rotational axis line of theworm wheel52bis perpendicular to the axis line of theworm shaft52aat a position displaced from the axis line of theworm shaft52a.

In other words, theelectric motor50 has an asymmetrical shape with respect to a motor virtual plane MP (seeFIG. 1) that passes through the axis line of theworm wheel52band is parallel to the axis line of theworm shaft52a.

Thehydraulic actuator unit1A according to the present embodiment further includes a following configuration in order to reduce the size of thehydraulic actuator unit1A as a whole, in a state where theelectric motors50 having such an asymmetrical structure is used and the member operatively connecting the first electric motor50(1) and the first variable displacement mechanism40(1) is configured identically with the member operatively connecting the second electric motor50(2) and the second variable displacement mechanism40(2).

As shown inFIGS. 1 and 3, thevariable displacement mechanism40 and theelectric motor cover70 have a symmetrical shape with respect to a first virtual plane P1 passing through the axis lines of the first control shaft41(1) and the second control shaft41(2) in a state where thevariable displacement mechanism40 and theelectric motor cover70 are attached directly or indirectly to thepump case30.

The first electric motor50(1) is attached to corresponding one (hereinafter, referred to as a first electric motor cover70(1) where appropriate) of the electric motor covers70 such that the electric motormain body51 thereof is located on one side of the first virtual plane P1 and on a side of the first control shaft41(1) that is opposite from the second control shaft41(2) to sandwich the first control shaft41(1) between the electric motormain body51 and the second control shaft41(2).

On the other hand, the second electric motor50(2) is attached to corresponding one (hereinafter, referred to as a second electric motor cover70(2) where appropriate) of the electric motor covers70 such that the electric motormain body51 thereof is located on the other side of the first virtual plane P1 and on a side of the second control shaft41(2) that is opposite from the first control shaft41(1) to sandwich the second control shaft41(2) between the electric motormain body51 and the first control shaft41(1).

In other words, a second hydraulic pump main body displacement operation assembly inclusive of the second electric motor50(2), corresponding one of themotor transmission mechanisms60 and the second electric motor cover70(2) is attached directly or indirectly to thepump case30 at a posture obtained by rotating a first hydraulic pump main body displacement operation assembly inclusive of corresponding one of themotor transmission mechanisms60 and the first electric motor cover70(1) by180 degrees about a virtual center line IC (seeFIG. 1) that is disposed parallel to the first and second control shafts41(1) and41(2) and is located at a center between the first and second control shafts41(1) and41(2).

Alternatively, the first and second electric motors50(1) and50(2) may be disposed on the same side of the first virtual plane P1 in a state where the first electric motor50(1) is disposed on a side of the first control shaft41(1) that is opposite from the second control shaft41(2) and the second electric motor50(2) is disposed on a side of the second control shaft41(2) that is opposite from the first control shaft41(1).

FIG. 10 is an end view, as viewed along the axes of the first control shaft41(1) and the second control shaft41(2), of ahydraulic actuator unit1B according to a modified example of the present embodiment.

FIG. 11 is a cross sectional view taken along line XI-XI indicated inFIG. 10.

In the drawings, the members identical with those of thehydraulic actuator unit1A according to the first embodiment are denoted by the identical reference numerals and detailed description thereof will not be repeatedly provided.

As shown inFIGS. 10 and 11, in thehydraulic actuator unit1B according to the modified example, the second hydraulic pump main body displacement operation assembly except for the second electric motor50(2) is attached directly or indirectly to thepump case30 at a posture obtained by rotating the first hydraulic pump main body displacement operation assembly except for the first electric motor50(1) by 180 degrees about the virtual center line IC. The first and second electric motors50(1) and50(2) are attached to the respective electric motor covers70 so as to be located on the same side of the first virtual plane P1.

More specifically, thehydraulic actuator unit1B according to the modified example has a pair of electric motor covers170 in place of the pair of electric motor covers70 in comparison with thehydraulic actuator unit1A according to the first embodiment.

One of the electric motor covers170 to which the first electric motor50(1) is attached will be referred to as a first electric motor cover170(1) and the other one of the electric motor covers170 to which the second electric motor50(2) is attached will be referred to as a second electric motor cover170(2), where appropriate.

Each of the electric motor covers170 in the modified example is configured such that both the lower surface of the electricmotor mount portion72 that faces thepump case30 and the upper surface that faces in an direction opposite from thepump case30 can serve as the electric motor mount surfaces.

More specifically, as shown inFIGS. 11,12A, and12B, the electricmotor mount portion72 is formed with an opening72apassing through from the upper to lower surfaces and has a size that allows the electricmotor output gear52dto be inserted therethrough.

In the case where theelectric motor50 is mounted on the upper surface of the electricmotor mount portion72, the electricmotor output gear52dis located on a side closer to the lower surface of the electricmotor mount portion72 through the opening72a.

In the modifiedhydraulic actuator unit1B including the electric motor covers170, the first electric motor50(1) is mounted on one of the upper and lower surfaces (the lower surface in the drawings) of the electricmotor mount portion72 of corresponding one of the electric motor covers170, while the second electric motor50(2) is mounted on the other one of the upper and lower surfaces (the upper surface in the drawings) of the electricmotor mount portion72 of corresponding one of the electric motor covers170, so that the first and second electric motors50(1) and50(2) are placed on the same side of the first virtual plane P1.

In the case where theelectric motor50 is mounted on the lower surface of the electricmotor mount portion72, the opening72ais preferably sealed by a lid member (not shown) which is attached to the upper surface of the electricmotor mount portion72.

As shown inFIGS. 3,10, and the like, in thehydraulic actuator unit1A according to the present embodiment and thehydraulic actuator unit1B according to the modified example, each of theengagement arms65 is located on a side of corresponding one of theoperation shafts62 that is opposite from thesector gear61 so that theoperation shafts62 is interposed between thesector gear61 and theengagement arms65.

In this configuration, the pair ofneutral springs120 can be disposed close to each other, so that it is possible to achieve reduction in size of the entirehydraulic actuator unit1A or1B including the pair ofneutral springs120.

As shown inFIGS. 4 and the like, in the present embodiment and the modified example, the pair ofneutral springs120 are configured integrally with each other by a single member.

Each of thehydraulic actuator unit1A according to the present embodiment and thehydraulic actuator unit1B according to the modified example is preferably applied to a riding mower.

FIG. 12A is a side view of a workingvehicle900A according to a first example.

FIG. 12B is a schematic view of anoperation unit800A included in the workingvehicle900A.

Further,FIG. 13 is a system block diagram of acontrol unit500 included in the workingvehicle900A.

As shown inFIG. 12A, the workingvehicle900A according to the first example is formed as a standing type riding mower.

More specifically, as shown inFIGS. 12A,12B, and13, the workingvehicle900A according to the first example includes avehicle frame910 provided with a driver'splatform911, thehydraulic actuator unit1A, anengine915, a first wheel motor unit920(1), a second wheel motor unit920(2), a pair of left and right driving wheels925(1) and925(2), acaster wheel930, amower unit935, theoperation unit800A, astarter916, apower generator unit917, abattery918, and thecontrol unit500. Theengine915 is supported by thevehicle frame910 and functions as a power source of the first and second hydraulic pump main bodies10(1) and10(2) of thehydraulic actuator unit1A. The first wheel motor unit920(1) has a hydraulic motor main body fluidly connected to the first hydraulic pump main body10(1) via the pair of first HST lines and is supported by thevehicle frame910 so as to be positioned on a first side in the vehicle width direction. The second wheel motor unit920(2) has a hydraulic motor main body fluidly connected to the second hydraulic pump main body10(2) via the pair of second HST lines and is supported by thevehicle frame910 so as to be positioned on a second side in the vehicle width direction. The pair of left and right driving wheels925(1) and925(2) are operatively driven by the first and second wheel motor units920(1) and920(2), respectively. Thecaster wheel930 is supported by thevehicle frame910. Themower unit935 is supported by thevehicle frame910 and is operatively driven by the drivingpower source915. Theoperation unit800A is fixed to thevehicle frame910 in a state capable of being manually operated by a driver standing on the driver'splatform911. Thestarter916 starts the drivingpower source915. Thepower generator unit917 generates electric power with use of rotational power of the drivingpower source915. Thebattery918 stores electric power generated by thepower generator unit917. Thecontrol unit500 controls actuation of the first and second electric motors50(1) and50(2).

As shown inFIG. 12A, in the workingvehicle900A according to the first example, theengine915 is of the horizontal type with the output shaft extending in the horizontal direction. Needless to say, the workingvehicle900A may alternatively adopt an engine of the vertical type with the output shaft extending in the vertical direction.

As shown inFIG. 12B, theoperation unit800A has a keyoperation input portion810 that is used to switch on/off the main power supply of the workingvehicle900A as well as to switch on/off thestarter916, and a pair of speedchange operating members820 that are used to operate the pair ofvariable displacement mechanisms40, respectively.

Hereinafter, where appropriate, one of the speedchange operating members820 used for operating the first variable displacement mechanism40(1) will be referred to as a first speed change operating member820(1) while the other one of the speedchange operating members820 used for operating the second variable displacement mechanism40(2) will be referred to as a second speed change operating member820(2).

The keyoperation input portion810 is configured such that a key inserted into the keyoperation input portion810 can be located at a main power supply off position, a main power supply on position and a starter on position, in accordance with driver manipulation.

As shown inFIG. 13, the position of the operated key is detected by a keyoperation position sensor815 that is included in the working vehicle.

In the workingvehicle900A according to the first example, the first and second speed change operating members820(1) and820(2) are each formed as a swing arm that is swingable about a rotational axis along the vehicle width direction.

FIGS. 12A and 12B also showstoppers821 that define the operable ranges of the first and second speed change operating members820(1) and820(2).

As shown inFIG. 13, positions (directions and amounts of operation) of the operated first and second speed change operating members820(1) and820(2) are detected by first and second speed change operating-side sensors825(1) and825(2) that are included in the workingvehicle900A.

Thecontrol unit500 performs control of the first and second electric motors50(1) and50(2) according to manual operation on the first and second speed change operating members820(1) and820(2) on the basis of signals from the first and second speed change operating-side sensors825(1) and825(2) as well as from the first and second speed change actuating-side sensors210(1) and210(2) which are included in thehydraulic actuator unit1A.

Theoperation unit800A of the workingvehicle900A according to the first example is further provided with a mower on/offmember830, a maximum-speed setting member840, amode switching member850, and aemergency stop member860.

FIG. 12B also shows anindicator890 for displaying errors as well as anindicator891 for displaying the amount of electric power stored in the battery.

The mower on/offmember830 is operated to drive or stop themower unit935.

More specifically, as shown inFIG. 13, the workingvehicle900A includes a mower on/offsensor835 that detects the operation state of the mower on/offmember830, amower clutch940 that is inserted in a working unit power transmission path from theengine915 to themower unit935, and a mowerelectric motor945 that actuates themower clutch940.

Thecontrol unit500 actuates the mowerelectric motor945 in accordance with manual operation of the mower on/offmember830 so as to engage or disengage themower clutch940.

The maximum-speed setting member840 is operated to set the maximum speed of the workingvehicle900A.

In other words, the maximum-speed setting member840 is used for setting an actuating amount of corresponding one of thevariable displacement mechanisms40 in a case where the first speed change operating member820(1) or the second speed change operating member820(2) is operated to the maximum level, so that the maximum speed of the workingvehicle900A is set.

More specifically, as shown inFIG. 13, the workingvehicle900A includes atop speed sensor845 that detects the position of the operated maximum-speed setting member840.

Thecontrol unit500 stores control data on the actuating amounts of the first and second electric motors50(1) and50(2) relative to the operating amounts of the first and second speed change operating members820(1) and820(2) for respective maximum speeds that can be set by the maximum-speed setting member840.

Thecontrol unit500 selects the control data corresponding to the position of the operated maximum-speed setting member840, and performs actuation control of the first and second electric motors50(1) and50(2) in accordance with manual operation on the first and second speed change operating members820(1) and820(2) with use of the selected control data.

Thecontrol unit500 preferably actuates the mowerelectric motor945 such that themower unit935 is stopped regardless of the operation state of the mower on/offmember830 in a case where a maximum speed exceeding a predetermined value is set by the maximum-speed setting member840.

FIG. 12B also shows a maximum-speed range841 in which themower unit935 can be driven.

Theemergency stop member860 is operated to forcibly stop theengine915 in emergencies.

When theemergency stop member860 is operated, theengine915 is forcibly stopped and the main power supply of the workingvehicle900A is forcibly switched off by way of thecontrol unit500.

Themode switching member850 is operated to change the actuating speeds of the first and second electric motors50(1) and50(2).

More specifically, as shown inFIG. 13, the workingvehicle900A includes amode switch sensor855 that detects the position of the operatedmode switching member850. Thecontrol unit500 switches the actuating speed of each of theelectric motors50 between a standard speed and a high speed, for example, on the basis of a signal transmitted from themode switch sensor855 according to manual operation on themode switching member850.

FIG. 13 also shows first and second axle sensors860(1) and860(2) that detect the rotational speeds of the pair of driving wheels925(1) and925(2), respectively.

Further shown inFIG. 13 is anengine output sensor865 that detects the rotational frequency of theengine915.

FIG. 14 is a side view of a workingvehicle900B according to a second example.

In the drawings, the members same as those in the workingvehicle900A according to the first example are denoted by the same reference numerals to omit detailed description thereof.

The workingvehicle900B according to the second example is different from the workingvehicle900A according to the first example in that theoperation unit800A is replaced by anoperation unit800B that is detachably connected to thevehicle frame910.

FIGS. 15A and 15B are schematic front and side views of theoperation unit800B, respectively.

Theoperation unit800B is different from theoperation unit800A in that the first and second speed change operating members820(1) and820(2) are replaced by a single speed change operating member820B.

More specifically, theoperation unit800B includes the keyoperation input portion810, the single speed change operating member820B, the mower on/offmember830, the maximum-speed setting member840 and theemergency stop member860.

FIG. 15A also shows anindicator892 for displaying vehicle traveling speed.

FIGS. 15A and 15B also show agrip bar822 that the driver can grip.

The single speed change operating member820B is in the form of a joy-stick capable of being slanted in a fore-and-aft direction and a lateral direction, as shown inFIG. 15B.

The workingvehicle900B according to the second example is provided with a single speed change operating-side sensor (not shown) in place of the first and second speed change operating-side sensors825(1) and825(2).

The single speed change operating-side sensor is configured to detect the position of the operated single speed change operating member820B (the position in the fore-and-aft direction as well as in the lateral direction).

Thecontrol unit500 controls the travel speed of the workingvehicle900B on the basis of the position in the fore-and-aft direction of the operated speed change operating member820B as well as controls left or right turn made by the workingvehicle900B on the basis of the position in the lateral direction of the speed change operating member820B.

More specifically, thecontrol unit500 calculates, on the basis of a signal from the speed change operating-side sensor, a reference actuation amount by which each of the first and second electric motors50(1) and50(2) is actuated by an identical amount in an identical direction in accordance with the position in the fore-and-aft direction of the operated speed change operating member820B. Thecontrol unit500 also calculates an actuation increase-decrease amount of each of the first and second electric motors50(1) and50(2) in accordance with the position in the lateral direction of the operated speed change operating member820B. Thecontrol unit500 controls to actuate each of the first and second electric motors50(1) and50(2) by each actuation amount that is calculated from the reference actuation amount and the actuation increase-decrease amount.

For example, in a case where the speed change operating member820B is operated left and forward, thecontrol unit500 calculates the reference actuation amount in accordance with the amount of forward operation of the speed change operating member820B as well as calculates the actuation increase-decrease amount in accordance with the amount of leftward operation of the speed change operating member820B. Thecontrol unit500 then outputs a control signal of an actuation amount obtained by subtracting the actuation increase-decrease amount from the reference actuation amount, to one of the first and second electric motors50(1) and50(2) corresponding to theleft driving wheel925. Thecontrol unit500 also outputs a control signal of an actuation amount obtained by adding the actuation increase-decrease amount to the reference actuation amount to the other one of theelectric motors50 corresponding theright driving wheel925. As a result, the workingvehicle900B turns left while traveling forward.

In a case where the speed change operating member820B is operated to the left in the center in the fore-and-aft direction, the reference actuation amount is made equal to zero. Thecontrol unit500 thus actuates one of theelectric motors50 corresponding to theleft driving wheel925 in the reverse-rotation direction by an amount corresponding to the actuation increase-decrease amount, as well as actuates the other one of theelectric motors50 corresponding to theright driving wheel925 in the normal-rotation direction by an amount corresponding to the actuation increase-decrease amount. As a result, the workingvehicle900B makes a zero turn in a leftward direction.

The above explained various operating members are of course electrically connected to thecontrol unit500 by wireless.

FIG. 16A is a side view of a working vehicle900C according to a third example.

FIG. 16B is a perspective view of anoperation unit800C in the working vehicle900C.

In the drawings, the members identical with those of the workingvehicles900A and900B according to the first and second examples are denoted by the identical reference numerals and detailed description thereof will not be repeatedly provided.

As shown inFIG. 16A, in the working vehicle900C according to the third example, theengine915 is of a vertical type in which its output shaft extends in a vertical direction.

The working vehicle900C according to the third example includes a pair of right and lefthandle rods912 that have proximal ends supported by thevehicle frame910 and free ends functioning as grip ends capable of being gripped by a driver, and theoperation unit800C mounted to the pair ofhandle rods912 in such a manner as to be positioned in the vicinity of the free ends of thehandle rods912.

Theoperation unit800C includes first and second speedchange operating members820C(1) and820C(2) that set only the respective operation amounts of the first and second variable displacement mechanisms40(1) and40(2), an outputdirection switching member821 C for switching the actuation directions of the first and second variable displacement mechanisms40(1) and40(2) (the slanted direction of themovable swash plates42 in thehydraulic actuator unit1 A according to the present embodiment), the mower on/offmember830 and theemergency stop member860.

The first and second speedchange operating members820C(1) and820C(2) are in the form of a swing arm capable of being rotated around respective rotational axis lines along the vehicle width direction.

The working vehicle according to the third example is provided with first and second speed change operating amount sensors (not shown) that detect the operated positions (operated amounts) of the first and second speedchange operating members820C(1) and820C(2), and an output direction sensor (not shown) that detects the operated position of the outputdirection switching member821C, in place of the first and second speed change operating-side sensors825(1) and825(2) that detect both of the respective operated directions and operated amounts.

Thecontrol unit500 actuates each of the first and second electric motors50(1) and50(2) by the amount according to a signal transmitted from each of the first and second speed change operation amount sensors in an actuation direction according to a signal transmitted from the output direction sensor.

In the working vehicle900C according to the third example, the mower on/offmember830 is in the form of a deadman type clutch.

Specifically, the mower on/offmember830 is in the form of a lever capable of being rotated around a rotational axis line along the vehicle width direction so as to be positioned at a clutch engagement position and a clutch release position that are close to and away from the grip portion, and is pressed toward the clutch release position by a biasing member.

FIG. 17 is a side view of the working vehicle900C according to the third example in a state of being changed to the manual mode.

As explained above, in order to change the hydraulic actuator unit from the electric mode to the manual mode, theelectric motor cover70 to which theelectric motor50 and the speed change actuating-side sensors210 are connected is detached, and theoperation rod130 is mounted.

In the manual mode, thecontrol unit500 should be of course inhibited to control actuations of theelectric motors50 based on signals transmitted from the speed change operating-side sensors825 and the speed change actuating-side sensors210.

For example, the working vehicle may be provided with a mode change switch (not shown) which can be manually operated by a driver or an electric motor mount sensor (not shown) which detects whether or not each of theelectric motors50 is mounted, so that thecontrol unit500 can recognize a change into the manual mode on the basis of a signal from the mode change switch or the electric motor mount sensor.

Alternatively, thecontrol unit500 may be configured to recognize a change into the manual mode in a case where a signal of an abnormal value is transmitted from the speed change actuating-side sensor210.

FIGS. 18A and 18B are front and side views of anoperation unit800D of a workingvehicle900D according to a fourth example, respectively.

In the drawings, the members identical with those of the workingvehicles900A to900C according to the first to third examples are denoted by the identical reference numerals and detailed description thereof will not be repeatedly provided.

The workingvehicle900D according to the fourth example includes a pair of right and left handle bars913 that have free ends functioning as grip portions, and theoperation unit800D is fixed in the vicinity of the free ends of the handle bars913.

In the workingvehicle900D according to the fourth example, the first and second speed change operating members820(1) and820(2) are inserted around the pair of right and left handle portions in a rotatable about the axis lines, respectively. The first and second speed change operating-side sensors825(1) and825(2) are configured so as to detect both the rotational directions and the rotational amounts around the respective axis line of the first and second speed change operating members820(1) and820(2), respectively.

FIGS. 18B also shows a secondemergency stop member861.

A second key is detachably mounted to the secondemergency stop member861. When the second key is detached from the secondemergency stop member861, theengine915 is forcibly stopped and the main power supply of the workingvehicle900D is forcibly switched off.

For example, the second key is connected to the driver through a string-like member so that unintentional fall of the driver out of the workingvehicle900D causes the second key to be detached from the secondemergency stop member861.

FIGS. 19A and 19B are plan and side views of a workingvehicle900E according to a fifth example, respectively.

In the drawings, the members identical with those of the workingvehicles900A to900D according to the first to fourth examples are denoted by the identical reference numerals and detailed description thereof will not be repeatedly provided.

As shown inFIGS. 19A and 19B, the workingvehicle900E according to the fifth example includes avehicle frame910E with a driver'sseat911E, theengine915, thehydraulic actuator unit1A, the first wheel motor unit920(1), the second wheel motor unit920(2), the pair of left and right driving wheels925(1) and925(2),non-driving wheels930 supported by thevehicle frame910E, themower unit935, the first and second speed change operating members820(1) and820(2), the starter (not shown), the power generator unit (not shown), the battery (not shown), and the control unit (not shown).

In the workingvehicle900E according to the fifth example, the non-driving wheel is in the form of caster wheel, and the first and second speed change operating members820(1) and820(2) are in the form of lever rotated around a rotational axis line along the vehicle width direction.

Although the engine is in the form of horizontal type in the workingvehicle900E according to the fifth example, it is of course possible to adopt the vertical type engine.

FIGS. 20A and 20B are plan and side views of a workingvehicle900F according to a sixth example, respectively.

In the drawings, the members identical with those of the workingvehicles900A to900E according to the first to fifth examples are denoted by the identical reference numerals and detailed description thereof will not be repeatedly provided.

The workingvehicle900F according to the sixth example is different from the workingvehicle900E according to the fifth example in that thehydraulic actuator unit1A is replaced by thehydraulic actuator unit1B according to the modified example.

FIG. 21 is a side view of a workingvehicle900G according to a seventh example.

In the drawing, the members identical with those of the workingvehicles900A to900F according to the first to sixth examples are denoted by the identical reference numerals and detailed description thereof will not be repeatedly provided.

The workingvehicle900G according to the seventh example is different from the workingvehicle900F according to the sixth example in that theengine915 is changed to the vertical type.

FIG. 22 is a side view of a workingvehicle900H according to an eighth example.

In the drawing, the members identical with those of the workingvehicles900A to900G according to the first to seventh examples are denoted by the identical reference numerals and detailed description thereof will not be repeatedly provided.

The workingvehicle900H according to the eighth example is different from the workingvehicle900E according to the fifth example in that theengine915 is changed to the vertical type and thenon-driving wheel930 is changed to asteering wheel930H that is steered by way of asteering wheel880.

The workingvehicle900H according to the eighth example includes a speedchange operating member820H for changing both of traveling direction and traveling speed in place of the first and second speedchange operating members820, in comparison with the working vehicle according to the fifth example.

In the workingvehicle900H according to the eighth example, thecontrol unit500 is configured to generate a difference between the actuation amounts of the first and second electric motors50(1) and50(2) in accordance with the turning angle of the vehicle in order to compensate a difference in the turning radius between the pair of driving wheels925(1) and925(2).

FIG. 23 is a side view of a workingvehicle9001 according to a ninth example.

In the drawing, the members identical with those of the workingvehicles900A to900H according to the first to eighth examples are denoted by the identical reference numerals and detailed description thereof will not be repeatedly provided.

The workingvehicle9001 according to the ninth example is different from the workingvehicle900H according to the eighth example in that the non-driving wheel is changed to thecaster wheel930,

In the workingvehicle9001 according to the ninth example, thecontrol unit500 generates a difference between the actuation amounts of the first and second electric motors50(1),50(2) in accordance with manual operation on thesteering wheel880 so that the workingvehicle9001 makes a turn.

The workingvehicle9001 according to the ninth example could make a zero turn by operating thesteering wheel880 in either right direction or left direction while operating the speedchange operating member820H at the neutral position.

Now, one example of a control program of thecontrol device500 in the working vehicle to which thehydraulic actuator unit1A according to the present embodiment is applied will be explained.

FIG. 24 is a flowchart of the control program according to the example.

The control program starts in response to a motion in which the key is operated to the main power supply on position so that the working vehicle is in a main power supply on state.

Thecontrol unit500 determines instep100 whether or not the key is located at the main power supply on position, and proceeds to step110 if YES while proceeding to step200 if NO.

Thecontrol unit500 determines instep200 whether or not the key is located at the starter on position, and proceeds to step210 if YES while returning to step100 if NO.

Thecontrol unit500 determines in thestep210 whether or not theengine915 can be turned over.

This determination may be made in accordance with an engine start program described inFIG. 25, for example.

More specifically, in a case where all the following conditions are satisfied, thecontrol unit500 turns on an engine start flag and proceeds to step220. On the other hand, in a case where any one of the conditions is not satisfied, thecontrol unit500 turns off the engine start flag and proceeds to step230. The above conditions are that there is no trouble in the various sensors as well as in the electric motors50 (step211), that a driver is riding on the driver'splatform911 or on the driver'sseat911E (step214), that each of the speedchange operating members820 is located at the neutral position (step215), that each of thevariable displacement mechanisms40 is in the neutral state (step218), and that a parking brake provided to the working vehicle is being actuated (step216).

Whether or not the driver is riding on either one of the driver'splatform911 and the driver'sseat911E is determined on the basis of a signal transmitted from a driver's platform/seat sensor870 (seeFIG. 13) which is included in the working vehicle.

Thecontrol unit500 determines in the step218 whether or not each of thevariable displacement mechanisms40 is in the neutral state on the basis of a signal from each of the speedchange operating members820. However, no signal is received from the speedchange operating members820 in the manual mode. Then, the determination made in the step218 always results in NO, and the engine cannot be started in the manual mode.

In view of the above problem, the engine start program includes, prior to the step218, step217 of determining whether or not the manual mode is currently selected.

More specifically, thecontrol unit500 is configured to bypass the step218 and to turn on the engine start flag if YES in the step217 (namely, in the manual mode).

Furthermore, the engine start program is configured to turn off the engine start flag in a case where theengine915 is not started despite the fact that thestarter916 has been driven for a predetermined period.

More specifically, the engine start program includes step212 of turning off the engine start flag in a case where a period st of continuously energizing thestarter916 exceeds a predetermined period x.

In order to prevent thestarter916 from being driven when the key is erroneously operated to the starter on position with theengine915 being driven, it is determined in the step212 whether the period st of continuously energizing thestarter916 satisfies st=0, 0<st<x, or x≦st.

In the case where st =0 is satisfied in the step212, thecontrol unit500 proceeds to step213 of determining whether or not theengine915 is stopped.

Thecontrol unit500 then turns on the engine start flag if YES in the step213 as well as if the remaining engine start conditions are satisfied, while turning off the engine start flag if NO in the step213.

More specifically, in a case where theengine915 is being stopped and the key is operated to the starter on position, thecontrol unit500 determines that st=0 is satisfied in the step212 and proceeds to the step213. Since theengine915 is being stopped in this case, thecontrol unit500 turns on the engine start flag if the remaining engine start conditions are satisfied.

To the contrary, in a case where the key is erroneously operated to the starter on position with theengine915 being driven, thecontrol unit500 determines NO in the step213 and turns off the engine start flag.

Furthermore, in the case where 0<st<x is satisfied in the step212, the engine start program bypasses the step213 and turns on the engine start flag if the remaining engine start conditions are satisfied.

This arrangement is made to prevent the engine start flag from being turned off in accordance with the determination in the step213 while theengine915 is being started up by thestarter916.

If YES in thestep210, thecontrol unit500 drives the starter to start the engine in step220.

If NO in thestep210, the program returns to START.

If YES in the step100 (in a case where theengine915 is being driven and the working vehicle is traveling), thecontrol unit500 proceeds to step110.

Thecontrol unit500 determines in thestep110 whether or not there is caused any error.

This determination may be performed by an error detection program described inFIG. 26, for example.

In a case where all the following conditions are satisfied, namely, that there is no trouble in the various sensors (step111), that there is no trouble in the electric motors50 (step112), and that a driver is riding on the driver'splatform911 or on the driver'sseat911E (step113), the error detection program turns off an error occurrence flag and proceeds to step120. On the other hand, if any one of the above conditions is not satisfied, the error detection program turns on the error occurrence flag and proceeds to step150.

If NO in the step110 (namely, in a case where there is caused an error), thecontrol unit500 forcibly stops to drive theengine915 in step150.

If YES in the step110 (namely, in a case where there is caused no error), thecontrol unit500 determines instep120 whether or not theengine915 is stopped.

Thestep120 is provided to check whether or not theengine915 is stalled due to some reason.

If NO in the step120 (namely, in a case where theengine915 is being properly driven), thecontrol unit500 proceeds to step140 and controls to actuate theelectric motors50 in accordance with manual operation of the speedchange operating members820 so as to actuate thevariable displacement mechanisms40.

On the other hand, if YES in the step120 (namely, in a case where the engine is being stalled), thecontrol unit500 actuates theelectric motors50 so as to bring thevariable displacement mechanisms40 into the neutral states.

More specifically, thecontrol unit500 determines instep130 whether or not thevariable displacement mechanisms40 are in the neutral state, and returns to START if YES in thestep130. On the other hand, if NO in thestep130, thecontrol unit500 proceeds to step131, actuates theelectric motors50 so as to bring thevariable displacement mechanisms40 into the neutral states, and then returns to START.

Thecontrol unit500 preferably actuates each of theelectric motors50 at a top actuating speed in thestep131.

The present embodiment exemplifies thehydraulic actuator unit1A that is formed as the hydraulic pump unit including the first and second hydraulic pump main bodies10(1) and10(2). However, the hydraulic actuator unit according to the present invention is of course not to be limited to the above.

Specifically, the hydraulic actuator unit according to the present invention can be embodied as a hydraulic pump unit including only a single hydraulic pump main body of the variable displacement type, a hydraulic motor unit including one or a plurality of variable displacement type hydraulic motor main bodies, or an HST unit including a hydraulic pump main body and a hydraulic motor main body at least one of which is of the variable displacement type.

Second Embodiment

Hereinafter, another embodiment of the hydraulic actuator unit according to the present application will be explained with reference to the accompanying drawings.

FIG. 27 is a plan view of ahydraulic actuator unit2 according to the present embodiment.

FIGS. 28 and 29 are cross sectional views taken along lines XXVIII-XXVIII and XXIX-XXIX inFIG. 27, respectively.

In the drawings, the members same as those in the first embodiment are denoted by the same reference numerals to omit detailed description thereof.

As shown inFIGS. 27 to 29, thehydraulic actuator unit2 according to the present embodiment is in the form of an axle driving device that integrally includes the hydraulic pumpmain body10 of variable displacement type and a hydraulic motormain body310 forming an HST in cooperation with the hydraulic pumpmain body10.

Theaxle driving unit2 is provided to each of the driving wheels of a working vehicle.

For example, as shown inFIG. 27, a working vehicle provided with a pair of right and left driving wheels includes a first axle driving unit2(1) that is configured identically with theaxle driving unit2 and drives one of the pair of driving wheels, and a second axle driving unit2(2) that is configured identically with theaxle driving unit2 and drives the other one of the pair of driving wheels.

As shown inFIGS. 27 to 29, theaxle driving device2 includes thepump shaft20 operatively connected to the driving power source, the hydraulic pumpmain body10 supported by thepump shaft10 in a relatively non-rotatable manner with respect thereto, thevariable displacement mechanism40 changing the suction/discharge amount of the hydraulic pumpmain body10, the hydraulic motormain body310 fluidly connected to the hydraulic pumpmain body10, amotor shaft320 supporting the hydraulic motormain body310 in a relatively non-rotatable manner with respect thereto, acenter section330, anaxle case340 accommodating the hydraulic pumpmain body10, the hydraulic motormain body310 and thecenter section330, anoutput shaft350 outputting rotational power, which has been operatively transmitted from themotor shaft320, toward the corresponding driving wheel, theelectric motor50, anelectric motor cover370 and themotor transmission mechanism60. The center section has apump surface330P with which the hydraulic pumpmain body10 is brought into contact in a sliding manner around the rotational axis line and amotor surface330M with which the hydraulic motormain body310 is brought into contact in a sliding manner around the rotational axis line, and is formed with a pair of HST operationfluid passages335 that fluidly connects the hydraulic pumpmain body10 and the hydraulic motormain body310. Theelectric motor cover370 is configured so that theelectric motor50 is detachably mounted thereto, and could be detachably mounted to theaxle case340 with theelectric motor50 being mounted thereto.

In the present embodiment, theaxle case340 is provided withboss portions345 so as to be positioned on both sides of themotor transmission mechanism60. Theelectric motor cover370 mounted to theboss portions345 with theelectric motor50 being mounted thereto.

Specifically, theboss portions345 are arranged around theoperation shaft62 in such a manner as to allow thesector gear61 and theengagement arm65 to extend radially outward with theoperation shaft62 as a reference.

In the present embodiment, as shown inFIG. 29, theboss portions345 are located on both sides of theoperation shaft62.

Theelectric motor cover370 includes the motor transmissionmechanism cover portion71, the electricmotor mount portion72 and theconnection portion73. Theelectric motor cover370 is detachably mounted to theaxle case340 through connection of theconnection portion73 to theboss portions345 by fasteningmembers79 such as bolts (seeFIG. 28).

Specifically, theelectric motor cover370 is substantially different from the electric motor covers70 only in that theside wall portion74 is deleted.

Theaxle case340 includes anupper housing341 and alower housing342 that are connected to each other in a separable manner along au up-and-down direction.

Thepump shaft20 is supported by the upper andlower housings341 and342 in a rotatable manner around the axis line along the vertical direction with its upper end being extended upward from theupper housing341.

The upper end of thepump shaft20 functions as the input end that is operatively connected the driving power source.

In the present embodiment, the cooling fan is supported on the upper end of thepump shaft20.

Thecenter section330 is accommodated in theaxle case340 in such a manner as that thepump surface330P faces upward and themotor surface330M faces toward the corresponding driving wheel.

Thevariable displacement mechanism40 includes thecontrol shaft41 and themovable swash plate42, as shown inFIG. 28.

Thecontrol shaft41 is supported by the axle case340 (theupper housing341 in the present embodiment) in a rotatable manner around the axis line along a substantially horizontal direction in a state where the first end41ais extended into theaxle case340 and the second ends is extended outward from theaxle case340.

In the present embodiment, the axle driving device is further provided with a speed-reduction gear mechanism360 that reduces rotational speed of the rotational power output by themotor shaft320 and transmits the rotational power whose rotational speed has been reduced to theoutput shaft350, abrake mechanism370 capable of selectively applying brake power to themotor shaft320, and thecharge pump90 that is operatively driven by thepump shaft20.

Claims (10)

The invention claimed is:

1. A hydraulic actuator unit comprising a pump case, first and second pump shafts that are supported by the pump case in a rotatable manner around respective axis lines in a state of being positioned in parallel to each other and being operatively connected to each other, first and second hydraulic pump main bodies that are accommodated in the pump case in a state of being supported by the first and second pump shafts respectively in a relatively non-rotatable manner with respect thereto, first and second variable displacement mechanisms that change displacements of the first and second hydraulic pump main bodies, respectively, and first and second electric motors that actuate the first and second variable displacement mechanisms, respectively, the hydraulic actuator unit being characterized in that,

the first pump shaft has first and second ends positioned on one and the other sides in its axis line direction, the first end being extended outward from the pump case to form an input end that is operatively connected to a driving power source,

the second pump shaft has first and second ends that are positioned on the same side as the first and second ends of the first pump shaft in the axis line direction, the second end being extended outward from the pump case to drive a cooling fan,

the first and second variable displacement mechanisms include first and second movable swash plates each of which changes a displacement of the corresponding hydraulic pump main body in accordance with its slanting position around a swing axis line, and first and second control shafts each of which is supported by the pump case in a rotatable manner around its axis line,

each of the first and second control shafts has a first end operatively connected to the corresponding movable swash plate in such a manner as to slant the movable swash plate in accordance with its rotation around the axis line and a second end extended outward from the pump case,

the first and second control shafts are supported by the pump case in such a manner as that they are orthogonal to the first and second pump shafts and their second ends are faced in the same direction to each other,

each of the pair of electric motors has an electric motor main body that is controlled and driven based on an external electric signal, an electric motor output mechanism that is operatively connected to an output shaft of the electric motor main body, and an electric motor case that supports the electric motor main body and the electric motor output mechanism,

the hydraulic actuator unit further includes a pair of electric motor covers for connecting the pair of electric motors to the pump case,

one of the pair of electric motors is mounted to one of the pair of electric motor covers to form a first electric motor assembly that is detachably mounted to the pump case so as to rotate the first control shaft around the axis line,

the other one of the pair of electric motors is mounted to the other one of the pair of electric motor covers to form a second electric motor assembly that is detachably mounted to the pump case so as to rotate the second control shaft around the axis line,

the first electric motor assembly is mounted to the pump case so that the corresponding electric motor has a rotational axis line in parallel with the first pump shaft in a state where the electric motor is positioned on an opposite side to the second control shaft with respect to the first control shaft and is also positioned on an opposite side to the first end of the first pump shaft with respect to a virtual plane that passes through the axis lines of the first and second control shafts, and

the second electric motor assembly is mounted to the pump case at a posture obtained by rotating the first electric motor assembly by 180 degrees about a virtual center line that is disposed in parallel with the first and second control shafts and is located at a center between the first and second control shafts, thereby the electric motor of the second electric motor assembly is positioned on an opposite side to the cooling fan with respect to the virtual plane.

2. A hydraulic actuator unit according toclaim 1, further comprising a pair of first spring pieces for holding the first control shaft at a neutral position around the axis line, a first engagement arm that is directly or indirectly supported by the first control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of first spring pieces, a pair of second spring pieces for holding the second control shaft at a neutral position around the axis line, and a second engagement arm that is directly or indirectly supported by the second control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of second spring pieces,

wherein the electric motor cover is provided with a prevention arm that pushes the corresponding pair of spring pieces apart from each other so that the corresponding engagement arm receives no influence from the pair of spring pieces upon mounting of the electric motor cover to the pump case.

3. A hydraulic actuator unit according toclaim 2, wherein the pair of first spring pieces and the pair of second spring pieces are directly or indirectly mounted to the pump case so as to be positioned between the first and second control shafts.

4. A hydraulic actuator unit according toclaim 3, further comprising a pair of sector gears that are supported by the corresponding control shafts in a relatively non-rotatable manner with respect thereto and are engaged with electric motor output gears of the corresponding electric motor output mechanisms,

wherein the engagement arm is integrally formed with a member forming the corresponding sector gear.

5. A hydraulic actuator unit according toclaim 1, wherein the electric motor output mechanism has a worm shaft that is operatively connected to the output shaft of the electric motor main body, a worm wheel that is engaged with the worm shaft, an electric motor output shaft that is supported by the electric motor case in a rotatable manner about its axis line and supports the worm wheel in a relatively non-rotatable manner with respect thereto, and an electric motor output gear that is supported by the electric motor output shaft in a relatively non-rotatable manner with respect thereto.

6. A hydraulic actuator unit according toclaim 1, wherein each of the electric motors is provided with a clutch structure that has a reverse-rotation preventing function of preventing the electric motor main body from being rotated by power applied from the electric motor output gear of the electric motor output mechanism while allowing the electric motor output gear to be rotated in accordance with rotation of the electric motor main body.

7. A hydraulic actuator unit comprising a pump case, a pump shaft that is supported by the pump case in a rotatable manner around its axis line, a hydraulic pump main body that is accommodated in the pump case in a state of being supported by the pump shaft in a relatively non-rotatable manner with respect thereto, a variable displacement mechanism that changes a displacement of the hydraulic pump main body, and an electric motor that actuates the variable displacement mechanism, the hydraulic actuator unit being characterized in that,

there is provided an electric motor cover to which the electric motor is mounted and which is detachably connected to the pump case with the electric motor being mounted thereto,

there is provided a motor transmission mechanism that operatively connects an electric motor output gear of the electric motor to a control shaft of the variable displacement mechanism upon mounting of an electric motor assembly, which is formed by the electric motor and the electric motor cover, to the pump case,

there are provided a pair of spring pieces that hold the control shaft at a neutral position around its axis line,

there is provided an engagement arm that is directly or indirectly supported by the control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of spring pieces, and

the electric motor cover is provided with a prevention arm that pushes the pair of spring pieces apart from each other so that the engagement arm receives no influence from the pair of spring pieces upon mounting of the electric motor cover to the pump case.

8. A hydraulic actuator unit according toclaim 7,

wherein the pump shaft includes first and second pump shafts that are arranged in parallel with each other and are operatively connected to each other, the hydraulic pump main body includes first and second hydraulic pump main bodies that are supported by the first and second pump shafts respectively in a relatively non-rotatable manner with respect thereto, the variable displacement mechanism includes first and second variable displacement mechanisms that change displacements of the first and second hydraulic pump main bodies, respectively, the electric motor includes first and second electric motors that have the same configuration to each other and actuate the first and second variable displacement mechanisms, respectively, the electric motor cover includes first and second electric motor covers that have the same configuration to each other and form first and second electric motor assemblies in cooperation with the first and second electric motors, respectively, the motor transmission mechanism includes first and second motor transmission mechanisms that have the same configuration to each other and operatively connect the electric motor output gears of the corresponding electric motors to the corresponding control shafts, respectively, the pair of spring pieces includes a pair of first spring pieces that hold a first control shaft of the first variable displacement mechanism at a neutral position around its axis line and a pair of second spring pieces that hold a second control shaft of the second variable displacement mechanism at a neutral position around its axis line, the engagement arm includes a first engagement arm that is directly or indirectly supported by the first control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of first spring pieces and a second engagement arm that is directly or indirectly supported by the second control shaft in a relatively non-rotatable manner with respect thereto so as to be sandwiched by the pair of second spring pieces, and the prevention arm includes a first prevention arm that is provided at the first electric motor cover so as to push the pair of first spring pieces apart from each other so that the first engagement arm receives no influence from the pair of first spring pieces upon mounting of the first electric motor cover to the pump case and a second prevention arm that is provided at the second electric motor cover so as to push the pair of second spring pieces apart from each other so that the second engagement arm receives no influence from the pair of second spring pieces upon mounting of the second electric motor cover to the pump case,

wherein the first and second control shafts are supported by the pump case in a rotatable manner around the respective axis lines in a state where they are parallel to each other and their ends that are operatively connected to the corresponding electric motors face in the same direction to each other,

wherein the first electric motor cover supports the first electric motor so as to be positioned on an opposite side to the second control shaft with respect to the first control shaft,

wherein the second electric motor cover supports the second electric motor so as to be positioned on an opposite side to the first control shaft with respect to the second control shaft, and

wherein the pair of first spring pieces and the pair of second spring pieces are positioned between the first and second control shafts.

9. A hydraulic actuator unit according toclaim 8,

wherein each of the first and second electric motors has an electric motor main body that is controlled and driven based on an external electric signal, an electric motor output mechanism that is operatively connected to an output shaft of the electric motor main body, and an electric motor case that supports the electric motor main body and the electric motor output mechanism, and

wherein the electric motor output mechanism has a worm shaft that is operatively connected to the output shaft of the electric motor main body, a worm wheel that is engaged with the worm shaft, an electric motor output shaft that is supported by the electric motor case in a rotatable manner about its axis line and supports the worm wheel in a relatively non-rotatable manner with respect thereto, and an electric motor output gear that is supported by the electric motor output shaft in a relatively non-rotatable manner with respect thereto and is operatively connected to the motor transmission mechanism.

10. A hydraulic actuator unit according toclaim 8, wherein each of the first and second electric motors has an electric motor main body that is controlled and driven based on an external electric signal, an electric motor output mechanism that is operatively connected to an output shaft of the electric motor main body, an electric motor case that supports the electric motor main body and the electric motor output mechanism, and a clutch structure that has a reverse-rotation preventing function of preventing the electric motor main body from being rotated by power applied from the electric motor output gear of the electric motor output mechanism while allowing the electric motor output gear to be rotated in accordance with rotation of the electric motor main body.

Images